ui: scroll to bottom when receiving activeBufferChanged signal

Triggers the ui manipulation code when the rootScope receives the signal.
Supports multiple ways of changing the buffer (clicking, shortcuts, etc.)
without having to duplicate this code.

js/websockets.js

@@ -430,6 +430,13 @@ weechat.controller('WeechatCtrl', ['$rootScope', '$scope', '$store', '$timeout',
     }
 
 
+    $rootScope.$on('activeBufferChanged', function() {
+        $rootScope.scrollToBottom();
+        document.getElementById('sendMessage').focus();
+        var ab = models.getActiveBuffer();
+        $rootScope.pageTitle = ab.shortName + ' | ' + ab.title;
+    });
+
     $scope.buffers = models.model.buffers;
     $scope.activeBuffer = models.getActiveBuffer
 
@@ -451,11 +458,6 @@ weechat.controller('WeechatCtrl', ['$rootScope', '$scope', '$store', '$timeout',
 
     $scope.setActiveBuffer = function(key) {
         models.setActiveBuffer(key);
-        $rootScope.scrollToBottom();
-        document.getElementById('sendMessage').focus();
-        var ab = models.getActiveBuffer();
-        $rootScope.pageTitle = ab.shortName + ' | ' + ab.title;
-
     };
 
     $rootScope.scrollToBottom = function() {